/*
 * [New BSD License]
 * Copyright (c) 2011-2012, Brackit Project Team <info@brackit.org>  
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Brackit Project Team nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.brackit.xquery.operator;

import org.brackit.xquery.ErrorCode;
import org.brackit.xquery.QueryContext;
import org.brackit.xquery.QueryException;
import org.brackit.xquery.Tuple;

/**
 * 
 * @author Sebastian Baechle
 * 
 */
public class Start implements Operator {
	public static class StartCursor implements Cursor {
		final Tuple start;
		boolean open = false;
		boolean deliver = false;

		public StartCursor(Tuple start) {
			this.start = start;
		}

		@Override
		public void close(QueryContext ctx) {
			open = false;
		}

		@Override
		public Tuple next(QueryContext ctx) throws QueryException {
			if (!open) {
				throw new QueryException(
						ErrorCode.BIT_DYN_RT_ILLEGAL_STATE_ERROR);
			}

			if (!deliver) {
				return null;
			}

			deliver = false;
			return start;
		}

		@Override
		public void open(QueryContext ctx) throws QueryException {
			open = true;
			deliver = true;
		}
	}

	public static class BufferStartCursor implements Cursor {
		Tuple[] buf;
		final int len;
		int pos = -1;

		public BufferStartCursor(Tuple[] buf, int len) {
			this.buf = buf;
			this.len = len;
		}

		@Override
		public void close(QueryContext ctx) {
			buf = null; // allow gc
			pos = -1;
		}

		@Override
		public Tuple next(QueryContext ctx) throws QueryException {
			if (pos < 0) {
				throw new QueryException(
						ErrorCode.BIT_DYN_RT_ILLEGAL_STATE_ERROR);
			}
			if (pos < len) {
				Tuple t = buf[pos];
				buf[pos++] = null; // allow gc
				return t;
			} else {
				return null;
			}
		}

		@Override
		public void open(QueryContext ctx) throws QueryException {
			pos = 0;
		}
	}

	@Override
	public Cursor create(QueryContext ctx, Tuple tuple) throws QueryException {
		return new StartCursor(tuple);
	}

	@Override
	public Cursor create(QueryContext ctx, Tuple[] buf, int len)
			throws QueryException {
		return new BufferStartCursor(buf, len);
	}

	@Override
	public int tupleWidth(int initSize) {
		return initSize;
	}
}